1. Field of the Invention
This invention relates to the manufacture of printed circuit boards and more particularly to the use of nickel as an etch resist in forming the conductive areas of the board.
2. Description of the Prior Art
In the past, printed circuit boards have been produced by a process in which the copper conductors were formed by coating the copper conductors and through-holes with nickel and subsequently plating a layer of gold thereon. The gold was used as an etch resist, after the application of which the excess copper was removed by etching. Since the etchant did not attack gold, the result of the process was a desired circuit configuration. Even when new etchants were developed which did not attack nickel, gold was used to provide solderability since nickel could not be soldered for mounting components on the board. This method was obviously expensive because of the heavy use of gold. As gold prices increased, the cost of board manufacture also increased.